I've Read somewhere that Fish stress can cause them do do erratic behaviour, including jumping. Things like Lack of O2 and whatnot.
I don't have much of a better explanation then that.
Far as fish acting strange. all the fish in my Fresh Tank started eating nothing near my filters last night..
Watching a movie, and all of a sudden I hear the Clicking noises they make when eating food of the surface... problem is.. I fed them a good 3 hours earlier..
Who knows.... Maybe they know something we dont.
-Paul